The main objectives of the proposed project are: (1) the elucidation of the cellular mechanism regulating the production of IgE antibodies with particular reference to the possibility of activating suppressor T cells involved in the abrogation of the IgE response, and (2) the development of an immunologically specific therapeutic regimen for the suppression of IgE antibodies by the use of chemically modified allergens capable of reversing the balance between TS and TH cells in favour of the former. On the basis of preliminary data obtained in the applicant's laboratory, it appears that administration of conjugates of allergenic molecules with isologous gamma-globulins or with high molecular weight polyethylene glycols results in the abrogation of the IgE response to the corresponding allergens in an immunologically specific manner and that this mode of immunosuppression involves the generation of appropriate suppressor T cells. Attempts will be made to fractionate the suppressor T cell population by discontinuous gradient centrifugation in order to isolate enriched suppressor cell fractions. Experiments will then be conducted to establish the Ly phenotype of these specifically induced suppressor cells using anti-Ly 1.2 and anti-Ly 2.2 antisera. It is also planned to establish if the suppressor T cells induced by these two distinctly different tolerogenic derivatives of the same antigen are directed to identical portions of the native antigen molecule possessing carrier properties. For the elucidation of this aspect, attempts will be made (a) to isolate the soluble suppressive factors from TS cells induced by either of these conjugates and (b) to establish if these factors compete in their binding for the same regions of an antigen molecule.